From publichealth.jhu.edu
Screening for mildly elevated blood sugar levels can help prevent the progression to type 2 diabetes and related complications
Is prediabetes a “real” clinical condition? It’s a matter of some debate among experts and doctors.
Even when it is recognized by clinicians, there is still disagreement about the criteria for diagnosis. But identifying prediabetes—a condition characterized by elevated blood sugar levels—opens an opportunity to prevent the progression to type 2 diabetes.
In a Q&A adapted from the April 2 episode of Public Health On Call, Elizabeth Selvin, PhD ’04, MPH, a professor in Epidemiology, unpacks the controversy around prediabetes and the value of lifestyle interventions in preventing diabetes and related health complications.
What is prediabetes?
Prediabetes is a term we use for individuals who are below the threshold for a diagnosis of type 2 diabetes but still have mildly elevated glucose levels and are thought to be at high risk for developing diabetes.
The entire concept of prediabetes is a bit controversial. There’s a lot of confusion about prediabetes, how to define it, and whether it is really a medical condition. I personally think prediabetes is real. I think it’s an important designation with important clinical relevance.
Why is a prediabetes diagnosis important to a patient’s health?
People diagnosed with prediabetes are at high risk for the development of diabetes and complications. From my perspective, prediabetes is an opportunity to identify people before the development of diabetes—it’s an opportunity to prevent weight gain, implement lifestyle interventions, and for people who are overweight or obese to lose weight.
A landmark randomized clinical trial called the Diabetes Prevention Program showed definitively that for people with elevated glucose, who are below the threshold for diabetes but likely to cross it, an intensive lifestyle intervention—weight loss, increased physical activity, and improved diet—prevents the progression to diabetes.
We also now have randomized clinical trials for pharmacologic therapies like GLP-1s, which are shown to prevent the progression from prediabetes to diabetes.
How is prediabetes diagnosed?
One of the problems in the field is that there are many definitions of prediabetes—there are five different definitions in current clinical use. That causes a lot of confusion because someone might have prediabetes by one definition but not by another.
Different organizations disagree on what’s best for defining prediabetes. Some measure fasting glucose; others measure hemoglobin A1C to assess hyperglycaemia. There is also a definition that measures two-hour glucose using a glucose tolerance test, which is not used much outside the setting of pregnancy.
The American Diabetes Association defines prediabetes as a fasting glucose of 100–125 milligrams per decilitre. A lot of people fall into that category. The WHO defines prediabetes as a fasting glucose of 110–125, so that’s a smaller group. Another definition uses haemoglobin A1C—usually an A1C of 5.7 to less than 6.5, while an international expert committee has said we should define prediabetes a little bit higher: from 6.0 to 6.4.
One of the key issues is that these definitions identify different people. If you’re using fasting glucose, you’ll get a different group of people. You can be prediabetic by the fasting glucose definition, but not by the A1C definition. I think that’s what causes a lot of confusion in the field.
Which definition do you recommend?
I’m an epidemiologist, so I say it depends. One nice thing about using A1C for diagnosing prediabetes or identifying people with prediabetes is that it’s a non-fasting test. That can really help in the context of screening and diagnosis: You don’t have to prepare for the clinic visit, and it doesn’t matter what you’ve eaten that day.
What does haemoglobin A1C measure?
It’s essentially a weighted average of elevations in glucose from the past two to three months. It gives a sense of chronic hyperglycaemia, or chronically elevated glucose. It’s a pretty stable test: Your haemoglobin A1C at one time is likely to be the same or very similar to your haemoglobin A1C measured at another time.
If your A1C is in the prediabetic range—or especially in the diabetic range—that means you’ve been having hyperglycaemia for a while and suggests that you’re potentially at high risk for developing diabetes.
Work from our group and many other groups has shown that people who have A1C in the prediabetic range are at an elevated risk for developing diabetes and complications from diabetes. Things like heart disease, kidney disease, and even overall mortality are elevated in people who have mildly elevated haemoglobin A1C. We know it’s a high-risk group, which is one reason I’m a big fan of haemoglobin A1C-based definitions.
What lifestyle changes should those with elevated haemoglobin A1C consider?
Diet, weight loss, and exercise can be helpful in slowing and preventing the progression to diabetes as people age. There’s very good evidence that modest weight loss—even 5% of body weight—can be effective and powerful for preventing progression to diabetes. One thing that gets lost in the discussion about weight loss is the prevention of weight gain. People tend to gain weight as they get older, so just preventing weight gain in the first place can be really important. [You can incorporate] modest lifestyle changes like eating a healthier diet and exercising—strength training and resistance training are really good for your muscles and help glucose metabolism.
https://publichealth.jhu.edu/2026/prediabetes-diagnoses-can-help-build-healthier-lifestyles
